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Abstract:

A process for joining a brass part and a silicone carbide ceramics part,
comprising steps of: providing a metal part made of brass, a ceramic part
made of silicone carbide ceramics, a titanium foil and a nickel foil;
bring the metal part, ceramic part, titanium foil and nickel foil into
contact, with the titanium and nickel foil inserted between the metal
part and ceramic part; applying a pressure of about 20 MPa˜60 MPa
to the parts to be joined; and simultaneously applying a pulse electric
current to the parts while the pressure is applied for heating up the
parts to a temperature of about 950° C. to about 1150° C.
at a rate of about 50° C./min˜300° C./min,
maintaining the temperature for about 20 minutes˜40 minutes.

Claims:

1. A process for joining a brass part and a silicone carbide ceramics
part, comprising steps of: parts comprising a brass part, a silicone
carbide ceramics part, a titanium foil and a nickel foil; bringing
surfaces of the silicone carbide ceramics part, the titanium foil, the
nickel foil and the brass part into contact in turn; applying a joining
pressure between about 20 MPa and 50 MPa to the parts; and simultaneously
applying a pulse electric current to the parts while the joining pressure
is applied, heating the parts at a rate below 50.degree. C./min when a
temperature of the parts is below about 300.degree. C.; when the
temperature of the parts is above about 300.degree. C., heating the parts
at a rate of about 80.about.200.degree. C./min until to a joining
temperature of about 750.degree. C. to about 950.degree. C., and
maintaining the joining temperature for about 10.about.35 minutes.

2. The process as claimed in claim 1, wherein the step of applying the
joining pressure further comprises placing the parts in a sintering
chamber of a spark plasma sintering device spark plasma sintering, the
joining pressure being applied to the parts through the upper pressing
head and the lower pressing head.

3. The process as claimed in claim 2, wherein the sintering chamber being
evacuated to a vacuum level of about 6 Pa to about 10 Pa.

4. The process as claimed in claim 2, wherein the spark plasma sintering
device has a DC pulse power, the upper pressing head and the lower
pressing head are respectively electrically connected with the positive
electrode and the negative electrode of the DC pulse power.

5. The process as claimed in claim 1, wherein the pulse electric current
applied to the metal part, ceramic part, and nickel foil is about
1000.about.8000 A with a pulse-width ratio of 6:1.

6. The process as claimed in claim 1, wherein both the nickel foil and
titanium foil have a thickness between about 0.1 mm and 0.5 mm.

7. The process as claimed in claim 1, wherein the process further
comprising polishing and activating the parts by cleaning with solution
containing hydrochloric acid or sulphuric acid, before the step of bring
into contact.

9. A composite article, comprising: a metal part made of brass; a ceramic
part made of silicone carbide ceramics; and a joining part, the joining
part including a first transition layer, a titanium layer, a second
transition layer, a nickel layer and a third transition layer; the first
transition layer located between the ceramics layer and the titanium
layer, the first transition layer substantially comprised of compounds of
titanium and carbon, and compounds of titanium and silicone; the second
transition layer located between the nickel layer and the titanium layer,
the second transition layer substantially comprised of intermetallic
compounds of nickel and titanium, and solid solutions of nickel and
titanium; the third transition layer located between the nickel layer and
the metal part, the third transition layer substantially comprised of
solid solutions of nickel and copper, and intermetallic compounds of
nickel and copper.

10. The composite article as claimed in claim 9, wherein the composite
article has a shear strength between 20 MPa and 50 MPa.

11. The composite article as claimed in claim 9, wherein the composite
article has a tensile strength between about 35 MPa and 70 MPa.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is related to co-pending U.S. patent
applications (Attorney Docket No. US36187), entitled "PROCESS FOR JOINING
BRASS PART AND SILICONE CARBIDE CERIMICS PART AND COMPOSITE ARTICLES MADE
BY SAME", by Zhang et al. This application has the same assignee as the
present application and has been concurrently filed herewith. The
above-identified applications are incorporated herein by reference.

BACKGROUND

[0002] 1. Technical Field

[0003] The exemplary disclosure generally relates to a process for joining
a metal part and a ceramic part, especially to a process for joining a
brass part and an silicone carbide ceramics part, and an article made by
the process.

[0004] 2. Description of Related Art

[0005] It is desirable to join brass parts and silicone carbide ceramics
parts. However, due to the two material having very different values for
distinct physical and chemical properties, such as thermal expansion, it
can be difficult to join brass and silicone carbide ceramics using
traditional bonding methods such as braze welding, fusion welding, and
solid diffusion bonding.

[0006] Therefore, there is room for improvement within the art.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Many aspects of the embodiments can be better understood with
reference to the following drawings. The components in the drawings are
not necessarily drawn to scale, the emphasis instead being placed upon
clearly illustrating the principles of the exemplary process for joining
brass part and silicone carbide ceramics part, and composite article made
by the process. Moreover, in the drawings like reference numerals
designate corresponding parts throughout the several views. Wherever
possible, the same reference numbers are used throughout the drawings to
refer to the same or like elements of an embodiment.

[0008] FIG. 1 is a schematic cross-sectional view of an example of a spark
plasma sintering device for implementing the present process.

[0009] FIG. 2 is a cross-sectional view of an exemplary embodiment of the
present article made by the present process.

DETAILED DESCRIPTION

[0010] The process according to the present disclosure is generally
implemented by a spark plasma sintering (SPS) device as illustrated in
FIG. 1.

[0011] Referring to FIGS. 1 and 2, an exemplary process for joining a
brass part and an silicone carbide ceramics part may include the least
the following steps.

[0012] A ceramic part 20 made of silicone carbide ceramics, a metal part
30 made of brass, and an intermediate layer 40 are provided. In this
exemplary embodiment, types of the brass may comprise alpha brass,
alpha-beta brass, beta brass, lead brass containing 1 wt %˜6 wt %
lead, tin brass containing 1 wt %˜6 wt % tin, aluminum brass
containing 1 wt %˜6 wt % aluminum, manganese brass containing 1 wt
%˜6 wt % manganese, iron brass containing 1 wt %˜6 wt % iron,
silicone brass containing 1 wt %˜6 wt % silicone, or nickel brass
containing 1 wt %˜6 wt % nickel. The intermediate layer 40 connects
together the surfaces of the metal part 30 and the ceramic part 20. The
intermediate layer 40 may include a titanium foil 41 and a nickel foil 43
stacked on the titanium foil 41. The titanium foil 41 is adjacent to the
ceramic part 20 and the nickel foil 43 is adjacent the metal part 30.
Each of the titanium foil 41 and the nickel foil 43 has a thickness of
about 0.1 mm˜0.5 mm. In this exemplary embodiment, the thickness of
the titanium foil 41 and the nickel foil 43 each may be about 0.1 mm,
0.15 mm, 0.25 mm, 0.35 mm, 0.4 mm, or 0.5 mm.

[0013] The metal part 30, ceramic part 20, and intermediate layer 40 are
pretreated. The pretreatment may include polishing the surfaces of the
metal part 30, ceramic part 20, and intermediate layer 40, by a 600
grit˜1000 grit abrasive paper. Then, the metal part 30, ceramic
part 20, and intermediate layer 40 may be activated through cleaning with
a solution containing hydrochloric acid or sulphuric acid. Then, the
metal part 30, ceramic part 20, and intermediate layer 40 are rinsed with
water and dried.

[0014] A mold 50 made of electroconductive material, such as graphite, is
provided as shown in FIG. 1. The mold 50 includes an upper pressing head
51, a lower pressing head 52, and a middle part 53. The middle part 53
defines a cavity (no shown) for accommodating the parts to be joined.

[0015] Subsequently, the metal part 30, ceramic part 20, and intermediate
layer 40 are placed into the mold 50 with the intermediate layer 40
inserted between the metal part 30 and the ceramic part 20, the titanium
foil 41 contacts the ceramic part 20 and the nickel layer 43, and the
nickel foil 43 contacts the titanium foil 41 and the metal part 30. The
upper pressing head 51 and the lower pressing head 52 from two opposite
sides, compress the metal part 30, ceramic part 20, and intermediate
layer 40 together.

[0016] A SPS device 10 is provided. The SPS device 10 includes a pressure
system 11 for providing pressure to the parts to be joined, a sintering
chamber 13, and a DC pulse power 14 for providing pulse current to the
parts and heating up the parts. The DC pulse power 14 includes a positive
electrode 16 and a negative electrode 17. The pulse-width ratio of the DC
pulse power 14 is 6:1, and the maximum amps of the DC pulse power 14 is
8000 A.

[0017] The mold 50 is placed in the sintering chamber 13. The upper
pressing head 51 and the lower pressing head 52 are electrically
connected to the positive electrode 16 and negative electrode 17 of the
DC pulse power 14. The sintering chamber 13 is evacuated to a vacuum
level between about 6 Pa and about 10 Pa. A pressure between about 20 MPa
and 50 MPa is then applied to the parts through the upper pressing head
51 and the lower pressing head 52. While the pressure is applied, a pulse
electric current between about 1000 A and 8000 A with a pulse-width ratio
of 6:1 is simultaneously applied to the parts, heating the parts at a
rate less than 50 degrees Celsius per minute (° C./min) when the
temperature of the parts are less than about 300° C., and heating
the parts at a rate of about 80° C./min˜200° C./min
when the temperature of the parts are above about 300° C. The
temperature of the parts is maintained at about 750°
C.˜950° C. for about 10 minute˜35 minutes, such as 10
minutes, 20 minutes or 35 minutes. Under the above mentioned conditions,
particles of the metal part 30, ceramic part 20, and intermediate layer
40 will react and fuse with each other to form a joining part 80 (shown
in FIG. 2) having multiple between the metal part 30 and the ceramic part
20. Thereby, the metal part 30 and the ceramic part 20 are joined via the
intermediate layer 40, forming a composite article 100.

[0018] Once the composite article 100 is cooled down, the composite
article 100 can be removed.

[0019] Owing to the present process, a permanent joint of great strength,
in this exemplary embodiment, a joining part 80 is obtained. The process
requires a short hold time and a low vacuum level of the sintering
chamber 13, thus significantly saves time and energy. Additionally,
coefficients of thermal expansion of the ceramic part 20, titanium foil
41, nickel foil 43, metal part 30 are gradually increased, i.e., a
coefficient of thermal expansion of the intermediate layer 40 is between
the coefficient of thermal expansion of the ceramics part 20 and the
coefficient of thermal expansion of the metal part 30 and gradually
changes from a value close to that of the ceramic part 20 in the area of
the bond of the ceramic part 20 and the joint part 80 to a value close to
that of the metal part 30 in the area of the bond of the joint part 80
with the metal part 30. Thus, thermal stress between the ceramics part 20
and metal part 30 can be reduced by the intermediate layer 40 thereby
improving the binding force between the ceramics part 20 and metal part
30 so the ceramics part 20 can be firmly joined with the metal part 30.

[0020] FIG. 2 shows a composite article 100 manufactured by the present
process. The composite article 100 includes the metal part 30, the
ceramic part 20, and multi-layered joining part 80 joining the metal part
30 and the ceramic part 20. The various layers of the joining layer 80
result from differing interaction between the metal part 30, titanium
layer 82, nickel layer 84, and ceramic part 20. In particular, the
joining layer 80 includes:

[0021] a) a first transition layer 81: The first transition layer 81 is
located between the ceramics layer 20 and the titanium layer 82. The
first transition layer 81 mainly includes compounds composited aluminum
element and carbon element, such as titanium carbide, and compounds
composited titanium element and silicone element, such as titanium
silicide, etc. This chemical results result from chemical reactions
between adjacent portions of the ceramics layer 20 and titanium layer 82;

[0022] b) a titanium layer 82: The titanium layer 82 results from portions
of the titanium layer 82 that do not react with either the ceramics layer
20 or the nickel layer 84;

[0023] c) a second transition layer 83: The second transition layer 83 is
located between the nickel layer 84 and the titanium layer 82. The second
transition layer 83 mainly includes chemical compounds comprising nickel
element and titanium element, and of nickel with titanium solid
solutions. The chemical results result from chemical reactions between
adjacent portions to the titanium layer 82 and the nickel layer 84;

[0024] d) a nickel layer 84: The nickel layer 84 results from portions of
the nickel layer 84 that do not react with either the titanium layer 82
or the ceramic part 20;

[0025] e) a third transition layer 85: The third transition layer 85 is
located between the nickel layer 84 and the metal part 30. The third
transition layer 85 mainly includes nickel with copper solid solutions,
and chemical compounds comprising nickel element and copper element. The
chemical results result from chemical reactions between adjacent portions
to the nickel layer 84 and the metal part 30.

[0026] The thermal expansion rate of the joining layer 80 gradually
changes from a value close to that of the ceramic part 20 (in the area of
81) to a value close to that of the metal part 30 (in the area of 85).
This results in a composite article well suited to temperature changes
due to the gradual, rather than abrupt, changes in its internal thermal
expansion rates.

[0027] Furthermore, the joining part 80 of the composite article 100 has
no crack or aperture, and has a smooth surface. The metal/ceramic
interface of the composite article 100 has a shear strength between about
20 MPa and 40 MPa, and a tensile strength between about 30 MPa and 60
MPa.

[0028] It is to be understood, however, that even through numerous
characteristics and advantages of the exemplary disclosure have been set
forth in the foregoing description, together with details of the system
and function of the disclosure, the disclosure is illustrative only, and
changes may be made in detail, especially in matters of shape, size, and
arrangement of parts within the principles of the disclosure to the full
extent indicated by the broad general meaning of the terms in which the
appended claims are expressed.